1. Field of the Invention
The present invention generally relates to heat recovery for the purpose of electrical or mechanical power generation. Specifically, the present invention is directed to various systems and methods for the conversion of heat of any quality into mechanical or electrical power.
2. Description of the Related Art
In general, there is a constant drive to increase the operating efficiency of power generation systems. By increasing the efficiency of such systems, capital costs may be reduced, more power may be generated and there may be a reduction of possible adverse impacts on the environment, e.g., a reduction in the amount of waste heat that must ultimately be absorbed by the environment. In other industrial processes, an excess amount of heat may be generated as a byproduct of the process. In many cases, such waste heat is normally absorbed by the environment through use of waste heat devices such as cooling towers.
There are several systems employed in various industries to produce useful work from a heat source. Such systems may including the following:
Heat Recovery Steam Generators (HRSG)—Typically, waste heat from gas turbines or other, similar, high quality heat sources is recovered using steam at multiple temperatures and pressures. Multiple operating levels are required because the temperature-enthalpy profile is not linear. That is, such prior art systems involve isothermal (constant temperature) boiling as the working fluid, i.e., water, is converted from a liquid to a vapor state. Various embodiments of the present invention eliminate the need for multiple levels and simplifies the process while having the capability to recover more heat and to economically recover heat from a much lower quality heat source.
Rankine Cycle—The classic Rankine cycle is utilized in conjunction with HRSGs to produce power. This process is complex and requires multiple steam turbines, feed water heaters, steam drums, pumps, etc. The methods and systems of the present invention are significantly less complex while being more effective than systems employing the Rankine cycle.
Organic Rankine Cycle—Similar to the classic Rankine cycle, an Organic Rankine cycle utilizes a low temperature working fluid such as isoButane or isoPentane in place of steam in the classic cycle. The system remains complex and is highly inefficient at low operating temperature differences.
Kalina Cycle—Dr. Kalina's cycle is a next generation enhancement to the Rankine cycle utilizing a binary fluid mixture, typically water and ammonia. Water and ammonia are utilized at different concentrations in various portions of the process to extend the temperature range potential of the cycle and to allow higher efficiencies than are possible in the Rankine cycle. The methods and systems of the present invention simplifies the process while having the capability to recover more heat and to recover heat from a low quality heat source.
The following patents may be descriptive of various aspects of the prior art: U.S. Pat. No., 5,029,444 to Kalina; U.S. Pat. No. 5,440,882 to Kalina; U.S. Pat. No. 5,095,708 to Kalina; U.S. Pat. No. 5,572,871 to Kalina; and U.S. Pat. No. 6,195,997 to Lewis; each of which are hereby incorporated by reference.
In general, what is desired are systems and methods for improving the efficiencies of various power generation systems and systems and methods for utilizing waste heat sources to improve operating efficiencies of various power and industrial systems. The present invention is directed to various systems and methods that may solve, or at least reduce, some or all of the aforementioned problems.